The invention relates to a woven webbing, particularly for automotive seat belts.
Woven webbing, also for use in automotive seat belts, is known from a wealth of publications and practical examples. In certain cases items are attached to one or more points of the webbing, whereby depending on how the items are attached this could result in the material of the webbing being weakened, thus resulting in the specified tensile strength of the webbing possibly no longer being satisfied over the full width in the scope as demanded. Such items are, for instance, retainer buttons for preventing movement, for example of a buckle, beyond the point of attachment. In addition, there are, for example, also microphones for automotive hands-off telephone systems which are attached to seat belts at one or more points. It is in this arrangement that the attachment damages threads, particularly warp threads, of the webbing to such an extent that the tensile strength of the webbing is reduced.
An object of the invention is to propose a woven webbing, particularly for automotive seat belts which is suitable for the attachment of applications in the run of the woven webbing, as well as such seat belt themselves in avoiding or at least greatly reducing the disadvantages known from prior art. This object is achieved with a woven webbing as it reads from claim 1. The first group of warp threads having a higher extensibility is provided to advantage in a portion in which application items are to be attached. Because of the higher extensibility of the corresponding warp threads any weakening and thus reduction in the tensile strength of the warp threads caused by the application items is now compensated such that both groups of warp threads feature the necessary tensile strength when the webbing is stressed. In this arrangement, the difference in the extensibility of the warp threads of the first group and the warp threads of the second group is selected to advantage so that when exposed to tensile stress all threads counter the tensile force uniformly. If, for instance, laser welding an application item, e.g. a microphone, to the woven webbing in accordance with the invention results in a weakening of the warp threads of the first group, this weakening now has no effect on proper functioning of the woven webbing, since the selected high extensibility of the warp threads of the first group compensates any weakening of the tensile strength.
In one advantageous further embodiment of the invention the woven webbing comprises warp threads of a third group comprising electrically conductive means. This now makes it possible to power electric devices attached at some location to the woven webbing in the sense of the warp threads of the first group; these electric devices may be, for example, microphones, sensors, controllers, and the like. In another advantageous further embodiment of the invention the warp threads of the first group comprise electrically conductive means in thus endowing the warp threads having a higher extensibility with a second function, namely the conduction of electricity. This combination of enhanced extensibility and conduction of electricity simplifies the structure of the woven webbing in accordance with the invention as a whole. In yet another advantageous further embodiment of the invention the electrically conductive means are electrically insulated at their surface. Now, the electrically conductive means can be routed very close together because of the individual insulation of the warp threads instead of having to rely on insulation due to a spacing even with electrically conductive warp threads spaced as viewed in the weft direction. It has been discovered to advantage that varnish coating the electrically conductive means can now be produced very cost-effectively and reliably in even attaining a color-matched varnish coating.
In a particularly advantageous further embodiment of the invention the woven webbing is configured so that the electrically conductive means are wound by the warp threads. This design of the warp threads wound with electrically conductive means has major advantages, especially in contraction and/or stretching of the woven webbing. The electrically conductive means spirally wound around the warp threads in accordance with the invention, for example, conducting wire with a rectangular cross-section complies with the lengthwise movements of the warp threads in their longitudinal direction without themselves being exposed to any appreciable tensile strength possibly tearing the electrically conductive means out of place. The pitch in the windings can be advantageously tailored to the particularly application concerned.
In one advantageous alternative in configuring the electrically conductive means arranged at the warp threads of the first group or third group it is now attained that a finely curled wire is arranged as the electrically conductive means within warp threads forming a staple common fiber. This design of the electrically conductive means also permits compensating contraction and/or stretching without ruining the electrically conductivity. In still another advantageous further embodiment the warp threads comprising electrically conductive means are “concealed” so-to-speak in the interior of the woven webbing. This has the major advantage that the electrically conductive means are now no longer visible whilst, on the other hand, being protected from wear and corrosion. In one additional advantageous further embodiment of the woven webbing in accordance with the invention one or more electrically device(s), especially microphone(s), sensor(s), controller(s) is/are applied to one or more locations in the region of the warp threads. This now makes it possible to apply an electrical device expediently for the application concerned at any location in the longitudinal run of the woven webbing; for example, a microphone for a hands-off telephone system, for a telephone or dictaphone, or a device for monitoring the health of the vehicle occupant such as pulse, temperature etc., or a lighting fixture or a loudspeaker. Further advantages and features read from the sub-claims.